The present invention relates to airfoils such as blades, vanes, struts or the like with aerodynamic surfaces, and to a method of fabricating such blades, vanes or struts. The invention has particular application to vanes of the type utilized in gas turbines used for aircraft propulsion.
Blades, vanes and struts of various airfoil design are commonly used in gas turbine engines. Typically, such blades, vanes or struts are solid members, since this affords the greatest combination of strength and ease of fabrication. However, a critical consideration in aircraft engine construction is weight reduction, which militates against the use of solid structural members. Accordingly, it is known to provide hollow blades, vanes or struts for such applications.
Since hollow airfoils do not have the same structural strength or stiffness as solid airfoils, it is necessary to provide hollow airfoils with some type of support such as stiffening ribs or the like. Heretofore, hollow airfoils with internal support structures have been disclosed, for example, in U.S. Pat. Nos. 3,365,124; 3,627,443 and 4,221,539. The construction of such hollow airfoils is relatively costly and complex. Typically, the airfoil is formed in two parts or halves, with the internal ribs being formed unitarily with one or both halves and joined together by suitable bonding techniques. Alternatively, the hollow airfoil shell would have to be fabricated first and then the internal rib structure inserted thereinto and bonded thereto.
Another important consideration in airfoils for turbo machinery is vibration damping. Such damping has been provided, for example, by external sheathing of the airfoil, as disclosed in U.S. Pat. No. 3,357,850. Such external sheathing necessitates additional manufacturing steps and can significantly increase the cost of the finished airfoil.